The present invention generally relates to systems for loading and/or unloading fluids for ships, commonly referred to as marine loading systems. These systems are used to transfer a fluid product between a ship and a quay or between two ships. Fluid product is understood to mean a liquid or gaseous product. More particularly, the present invention concerns a device for providing information on positioning of a coupling and for alarm provision, for the movement of such a loading and/or unloading system.
Generally, marine loading systems have a fluid transfer line end that is fixed to a base and connected to a tank of fluid to be transferred, and an opposite line end that is moveable and provided with a coupling adapted for connecting to a target duct, itself connected to a fluid tank.
The movement of the moveable coupling is controlled by actuators which are themselves controlled by a control device that is controlled by an operator. When the coupling is moved too far from the base, there is a risk of damage to the system, in particular by rupture or interference. When the coupling is moved too far from the base during extension there is a risk of rupture of the system. When the coupling is rotated relative to the base, in particular when several loading systems are disposed in parallel on a quay, there is a risk of collision with the neighboring loading systems: the term damage by interference is used. Furthermore, there is a risk of rupture on rotation.
To avoid the damage or rupture of the marine loading system, alarm devices have been provided on certain types of loading devices.
In general terms, the present invention aims to improve these alarm devices for fluid loading devices for ships.
Two families of fluid loading systems for ships are known, which are distinguished by their structure: systems for transfer by rigid pipes and systems for transfer by flexible pipes. In the family of systems for transfer by rigid pipes, loading arm systems and pantograph systems can be distinguished.
The loading arm is an articulated tubing arrangement, having a base, connected to fluid tank, on which there is mounted a first pipe, designated inner pipe, via a portion of tube with a 90° bend enabling rotation of one of its ends about a vertical axis, and the other end about a horizontal axis. At the opposite end of the inner tube, a second pipe, designated the outer pipe, is rotatably mounted about a horizontal axis. A coupling is mounted at the end of the outer pipe. Each of the three rotations is controlled by a jack or hydraulic motor.
In the case of loading arms, the use of proximity detectors is known for triggering alarms. These proximity detectors are placed at the base for the alarms concerning the rotation of the inner pipe relative to the base, and on the inner and outer tube to trigger alarms during extension of the loading arm. In practice, the operation of such proximity detectors is simple: a cam, mounted on a member of the loading arm, passes in front of a corresponding proximity detector, itself attached to another member of the loading arm, which triggers one or more alarms. According to the positioning of the sensors, the alarm is triggered for example when the system is too extended or has too high an angle relative to the base.
This type of detector only gives information of on-off type, that is to say that the alarms are triggered when the operator makes the loading arm leave a predefined zone, designated working zone. In other words, the operator is informed by an alarm only when he goes outside the working zone but has no information when he is within said working zone, or near the limit of the working zone.
Another system known for a loading arm comprises angle sensors disposed on different moveable members of the loading arm. This makes it possible to know at any time the relative angles of each member of the loading arm relative to a neighboring member or relative to the vertical, by using pendulum sensors, and to determine thereby the position of the coupling relative to the base, and to deduce therefrom whether it is necessary to trigger an alarm or not.
These alarm devices enable an alarm to be triggered with a greater or lesser degree of alert, and furthermore, in certain cases, enable emergency sequences to be triggered. Moreover, these devices enable alarms or emergency sequences to be triggered in anticipation, when the loading arm approaches the limit of the working zone at a speed greater than a predetermined speed.
The pantograph systems, like the loading arms, have a base connected to a tank. A crane is rotatably mounted on that base. The crane has a boom carrying a pipe for the fluid. At the end of the boom there is mounted a pantograph composed of articulated pipes for the fluid, and enabling a coupling to be moved that is mounted at the free end of the pantograph. The inclination of the pantograph is controlled by a rotation at the end of the boom. The movement of the pantograph is controlled by hydraulic motors and by a jack for the rotation on the base.
In the case of pantograph systems, the use of systems triggered by proximity sensors is known for the rotation relative to the base and by wire or incremental sensor for the length along the boom and the unfolded length of the pantograph.
Generally, alarm devices for loading systems with rigid piping have other drawbacks.
The loading system must imperatively have a structure with precise kinematics known in advance in order to be able to judiciously locate thereon angle and position sensors and/or overshoot sensors.
It is necessary to locate sensors between each articulated member from the base to the coupling to obtain information on positioning of the coupling relative to the base. The sensors thus depend on the structure of the loading system. The cumulative error of this “chain” of sensors has a negative impact on the precision of the positioning of the coupling.
Lastly, the flexible piping systems generally have a line in which is conveyed the fluid product and a mechanical system enabling the line to be maneuvered. There are several types of maneuvering systems, but in all cases they include a manipulating crane or structure which supports the coupling for connecting the flexible piping.
To date, no distance measuring system exists enabling alarms to be triggered for the systems with flexible piping.